Before filling up the sprayer, check your water quality.
Spraying with hard water might still give you a kill, however, as former University of Saskatchewan professor Les Henry says, it may be “a lot less zippy than it could be.”
Hard water, with high magnesium and calcium levels, is common in Saskatchewan because many wells tap into glacial deposits. Glyphosate binds to magnesium and calcium and becomes inactive.
Farmers, custom sprayers and crop consultants can purchase Hach kits from water well supply stores to measure hardness in well water, dugouts, and sloughs. A water well analysis should assign a value to hardness as well.
As a guideline, water with 20 grains per U.S. gallon is too hard to use with low glyphosate rates, and 40 grains per gallon isn’t recommended for high glyphosate rates. Water with 35 grains per gallon also renders 2,4-D amine nearly useless. But 2,4-D ester isn’t affected by hard water.
It’s not always possible to find an ideal water source to mix with glyphosate.
“If you have shaky water, the less volume you use the better. Now, if you’re in some kind of situation where coverage is important or something like that, that might be another issue. But the higher volume results in more antagonism,” says Henry.
Farmers using hard water should not cut glyphosate rates.